In recent years, systems for implementing a conference between remote sites such as video conference systems or the like have become widespread. Among such systems, a system in which a display screen common to a plurality of terminals (for example, personal computers (PCs)) connected via a network is displayed, and each terminal is able to perform a manipulation on a display object displayed on the display screen, so that the display screen can be shared among the terminals is known. For example, an example of a system in which a display screen can be shared among a plurality of terminals connected via a network is disclosed in Patent Literature 1.